AutomationElement.GetCurrentPattern(AutomationPattern) 方法

定义

命名空间:

System.Windows.Automation

程序集:

UIAutomationClient.dll

检索此 AutomationElement 上的指定模式对象。

public:
 System::Object ^ GetCurrentPattern(System::Windows::Automation::AutomationPattern ^ pattern);

public object GetCurrentPattern (System.Windows.Automation.AutomationPattern pattern);

member this.GetCurrentPattern : System.Windows.Automation.AutomationPattern -> obj

Public Function GetCurrentPattern (pattern As AutomationPattern) As Object

参数

pattern

AutomationPattern

要检索的模式的标识符。

返回

Object

模式对象（如果 AutomationElement 当前支持指定的模式）。

例外

InvalidOperationException

该元素不支持此模式。

ElementNotAvailableException

AutomationElement 的 UI 不再存在。

示例

下面的示例演示如何使用此方法检索一个 SelectionItemPattern，然后用于在列表框中选择项。

/// <summary>
/// Sets the focus to a list and selects a string item in that list.
/// </summary>
/// <param name="listElement">The list element.</param>
/// <param name="itemText">The text to select.</param>
/// <remarks>
/// This deselects any currently selected items. To add the item to the current selection 
/// in a multiselect list, use AddToSelection instead of Select.
/// </remarks>
public void SelectListItem(AutomationElement listElement, String itemText)
{
    if ((listElement == null) || (itemText == ""))
    {
        throw new ArgumentException("Argument cannot be null or empty.");
    }
    listElement.SetFocus();
    Condition cond = new PropertyCondition(
        AutomationElement.NameProperty, itemText, PropertyConditionFlags.IgnoreCase);
    AutomationElement elementItem = listElement.FindFirst(TreeScope.Children, cond);
    if (elementItem != null)
    {
        SelectionItemPattern pattern;
        try
        {
            pattern = elementItem.GetCurrentPattern(SelectionItemPattern.Pattern) as SelectionItemPattern;
        }
        catch (InvalidOperationException ex)
        {
            Console.WriteLine(ex.Message);  // Most likely "Pattern not supported."
            return;
        }
        pattern.Select();
    }
}

''' <summary>
''' Sets the focus to a list and selects a string item in that list.
''' </summary>
''' <param name="listElement">The list element.</param>
''' <param name="itemText">The text to select.</param>
''' <remarks>
''' This deselects any currently selected items. To add the item to the current selection 
''' in a multiselect list, use AddToSelection instead of Select.
''' </remarks>
Public Sub SelectListItem(ByVal listElement As AutomationElement, ByVal itemText As String)
    If listElement Is Nothing OrElse itemText = "" Then
        Throw New ArgumentException("Argument cannot be null or empty.")
    End If
    listElement.SetFocus()
    Dim cond As New PropertyCondition(AutomationElement.NameProperty, itemText, PropertyConditionFlags.IgnoreCase)
    Dim elementItem As AutomationElement = listElement.FindFirst(TreeScope.Children, cond)
    If Not (elementItem Is Nothing) Then
        Dim pattern As SelectionItemPattern
        Try
            pattern = DirectCast(elementItem.GetCurrentPattern(SelectionItemPattern.Pattern), _
                SelectionItemPattern)
        Catch ex As InvalidOperationException
            Console.WriteLine(ex.Message) ' Most likely "Pattern not supported."
            Return
        End Try
        pattern.Select()
    End If

End Sub

备注

对于经常重复的任务（如示例中的一个任务），缓存模式和使用 GetCachedPattern会更高效。

注解

GetCurrentPattern 根据调用时的可用性获取指定的模式。

对于某些形式的 UI，此方法会产生跨进程性能开销。 应用程序可以通过缓存模式，然后使用它们 GetCachedPattern来集中开销。

另请参阅

• 客户端的 UI 自动化控件模式